Corner bead products are used in wall finishing for both aesthetics and utility. They finish a rough corner into a pleasing symmetrical transition with the respective adjoining walls, and also provide some resistance to abuse and impact on the corner. To accomplish these tasks, a suitable corner bead product should fit snugly on the wall, be easy to attach, and have material and design properties that allow it to resist at least minor impacts without severe damage or detachment from the wall.
An important feature of prior art metal corner bead is a slightly rounded corner that protrudes from the actual corner of the part. This feature is also known as the “bead”, but for purposes of describing the invention, it will be referred to as the “corner rib”. In metal corner bead, the rib aids in the finishing of the corner by allowing the finisher to easily apply some significant “fill” of joint compound all the way up to the corner. The rib has a radius of just 0.03-1.10 inch (0.08-2.79 cm) and a preferred maximum height above the corner bead flanges of 0.015-0.024 inch (0.04-0.06 cm), so the surface of the rib itself that is not covered by joint compound is easily painted over for a pleasing finish. If the corner bead simply has a sharp 90° angle at the corner, it is much more difficult to apply a thin layer of joint compound that covers the bead in close proximity to the actual corner and in a way that is able to be sanded to a smooth, paintable finish.
It is known that the core material of corner bead can be plastic, as well as metal. Conventional corner bead products made from steel or aluminum are easily dented upon moderate impact. Known plastic corner bead products typically possess a sharp angle or corner on the spine and are more flexible and less easily dented, but they tend to crack at the corner when held in place by rigid fasteners, or often pull away from the wall when held in place by adhesive or joint compound.